1. Field of the Invention
This invention relates to the welding of pipes under conditions which require exclusion of the atmosphere from the interior of the pipe, and more particularly to a system of this character which can be used on pipes of differing sizes.
2. Description of the Prior Art
The term "prior art" as used herein, or in any statement by or on behalf of applicant means only that any document or thing referred to as prior art bears, directly or inferentially, a date which is earlier than the effective filing date hereof.
When welding pipes together under conditions requiring exclusion of the atmosphere, the weld site and the interior of the pipes are flushed with an inert gas such as argon and/or nitrogen. These gases are commonly referred to as "purge" gases vicinity of the weld. For example, when making a TIG or Tungsten Inert Gas weld, the welding torch has a concentric sleeve surrounding the electrode through which argon under pressure is supplied to the weld site. This flow of argon excludes the atmosphere from the weld arc. In order to exclude atmosphere from the side of the weld site opposite to the torch, purge gas under pressure, such as argon, is used to drive the oxygen-bearing atmosphere from the interior of the pipes being welded and to maintain an oxygen-free condition at the weld site.
When using purge gases, welders commonly blank off open pipe ends with sheet materials at hand such as wood, metal and even cardboard. Typically, the sheet material is not held firmly in place and often blows off the open pipe end because of the pressure of purge gas within the pipe.
Various devices have been proposed for closing off open pipe ends for a variety of purposes other than purge gas welding. For instance, U.S. Pat. No. 2,810,401 to Burton J. Stansbury shows a pipe end closure used to keep children and animals from crawling into the open pipe end when it is left unguarded overnight. The Stansbury device has a toggle system internally of the pipe which moves outwardly as a key outside the closure is rotated to turn a threaded shaft on which a follower connected to the toggle arms moves. The Stansbury device is not gas-tight and the closure member, which is in the form of a shallow cup, can be used only with one size of pipe.
Other pipe closures utilize expandable members of resilient material (such as U.S. Pat. Nos. 3,550,636 and 3,577,737). These do not close off the pipe at its open end, but rather a spaced distance internally therefrom and require relatively enormous expanding pressure to remain in place by friction alone against pressure of fluids trying to escape from the pipe through the open end.
U.S. Pat. No. 2,256,775 to Alfred W. Hubbell shows a pipeline plug insertable in a pipeline "to effeotively seal the line against flow from downstream side thereof while repairs are being made." This device is urged through the line by the application of fluid pressure upon its upstream side.
U.S. Pat. No. 4,316,487 shows a "tubular obturator" for closing a pipeline when it is desired to subject the pipeline to a pressure test. This device expands internally of the pipe to hold the device in place by friction.
U.S. Pat. No. 4,285,368 to Garrett D. Terrill, et al. shows a specialized closure insertable in a special fitting having a general tubular portion extending transverse to the axis of the pipeline.
U.S. Pat. No. 4,494,584 shows an internal radially-expandable plug for sealing one section of a pipe from another to prevent different fluids in the different sections from mixing.
It is believed that the patents discussed above contain information which is or might be considered to be material to the examination of this application. These patents are believed to be relevant to the present invention because they were adduced by a prior art search made by an independent searcher. A copy of each of the above-listed patents is supplied to the Patent and Trademark Office herewith.
No representation or admission is made that any of the above-listed documents is part of the prior art, in any acceptation of that term, or that no more pertinent information exists.